1. Field of the Invention
This invention relates to aqueous liquid compositions suitable for forming a protective coating containing an organic binder material on metal surfaces that are contacted with the compositions, either by direct deposition of a protective film on the metal while the liquid composition is in contact with the metal, or, more commonly, by depositing a liquid film of the liquid composition on the metal and converting this liquid film to a protective solid film by removing water from the initially deposited liquid film and, optionally, heating or otherwise causing the solid constituents of the liquid film to coalesce and/or react, so as to produce an adherent solid film on the metal surface. The solid film thus deposited may be protective against corrosion, damage during cold working of the underlying metal, or the like. The metal surfaces processed as described above may or may not have other surface layers, such as phosphate or chromate conversion coatings, coatings formed by anodization, or the like, underlying the coating produced on the surface by using this invention.
2. Statement of Related Art
Many aqueous liquid compositions that deposit protective coatings on metal surfaces are known. Little prior attention appears to have been paid, however, to the potential of such aqueous liquid compositions for damaging, during treatment, the surfaces that they are intended to protect.